import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        int n = in.nextInt();
        char[] s = in.next().toCharArray();

        char maxChar = '0';
        int maxCount = 0;
        int[] hash = new int[26];
        for (int i = 0; i < n; i++) {
            char ch = s[i];
            if(++hash[ch - 'a'] > maxCount){
                maxChar = ch;
                maxCount = hash[ch - 'a'];
            }
        }
        if(maxCount > (n + 1) / 2){
            System.out.println("no");
        }else{
            System.out.println("yes");
            char[] ret = new char[n];
            int i = 0;
            while (maxCount -- != 0){
                ret[i] = maxChar;
                i += 2;
            }
            for (int j = 0; j < 26; j++) {
                if(hash[j] != 0 && (char) j + 'a' != maxChar){
                    while(hash[j] -- != 0){
                        if(i >= n) i = 1;
                        ret[i] = (char) ((char) j + 'a');
                        i += 2;
                    }
                }
            }
            for (int j = 0; j < n; j++) {
                System.out.print(ret[j]);
            }
        }
    }
}